public class linkedList implements IList{

    public class ListNode{
        int val;
        public ListNode next;
        public ListNode prev;
        public ListNode(int val) {
            this.val = val;
        }
    }


    public ListNode head;
    public ListNode last;
    @Override
    public void display() {
        ListNode cur = head;
        while(cur != null) {
            System.out.print(cur.val +" ");
            cur = cur.next;
        }
    }

    @Override
    public int size() {
        int count = 0;
        ListNode cur = head;
        while(cur != null) {
            count++;
            cur = cur.next;
        }
        return count;
    }

    @Override
    public boolean contains(int key) {
        ListNode cur = head;
        while(cur != null) {
            if(cur.val == key) {
                return true;
            }
        }
        return false;
    }

    @Override
    public void addFirst(int data) {
    ListNode node = new ListNode(data);
    if(head == null) {
        head = node;
        last = node;
    }else {
        node.next = head;
        head.prev = node;
        head = node;
    }
    }

    @Override
    public void addLast(int data) {

      ListNode node = new ListNode(data);
      if(head == null) {
          head = node;
          last = node;
      }else {
          last.next = node;
          node.prev = last;
          last = node;
      }
    }

    @Override
    public void addIndex(int index,int data) {
        if(index < 0 || index > size()) {
            throw new IndexException("双向链表，index不合法"+index);
        }
        if(index == 0) {
            addFirst(data);
            return;
        }
        if(index == size()) {
            addLast(data);
            return;
        }
        ListNode node = new ListNode(data);
        ListNode cur = findIndex(index);
        node.next = cur;
        cur.prev.next = node;
        node.prev = cur.prev;
        cur.prev = node;
    }

    @Override
    public void remove(int key) {
        ListNode cur = head;
        while(cur != null) {
            if(cur.val == key) {
                    if (cur == head) {
                       head = head.next;
                       if(head != null) {
                           head.prev = null;
                       }else {
                           //只有一个节点 且是需要删除的节点
                           last = null;
                       }
                    }else{
                        cur.prev.next = cur.next;
                      if(cur.next != null) {
                          cur.next.prev = cur.prev;
                          //cur.prev.next = cur.next;
                      }else {
                          //删除尾巴节点
                         // cur.prev.next = cur.next;
                          //cur.prev.next = null; => cur.prev.next = cur.next;
                          last = last.prev;
                      }
                }
              return;
            }
            cur = cur.next;
        }
    }

    @Override
    public void removeAll(int key) {
        ListNode cur = head;
        while(cur != null) {
            if(cur.val == key) {
                if (cur == head) {
                    head = head.next;
                    if(head != null) {
                        head.prev = null;
                    }else {
                        //只有一个节点 且是需要删除的节点
                        last = null;
                    }
                }else{
                    cur.prev.next = cur.next;
                    if(cur.next != null) {
                        cur.next.prev = cur.prev;
                        //cur.prev.next = cur.next;
                    }else {
                        //删除尾巴节点
                        // cur.prev.next = cur.next;
                        //cur.prev.next = null; => cur.prev.next = cur.next;
                        last = last.prev;
                    }
                }
            }
            cur = cur.next;
        }
    }

    @Override
    public void clear() {
       this.head = null;
       this.last = null;
    }

    private ListNode findIndex(int index) {
        ListNode cur = head;
        while(index != 0) {
            cur = cur.next;
            index --;
        }
        return cur;
    }

}
